209818domain: NAppears in sequencesarctan(arcsinh(x)*tan(x))=2/2!*x^2+4/4!*x^4-130/6!*x^6-6232/8!*x^8...at n=4A012614Number of nonisomorphic n-element self-dual posets (or partially ordered sets).at n=11A133983Expansion of Product_{k>=1} (1+x^k)^k / (1-x^k).at n=20A262667